The present invention relates to a magnetic head arm composed of magnetic head assemblies which are attached to an actuator assembly, a method of producing a magnetic head arm and an apparatus for producing a magnetic head arm and, more particularly, to a magnetic head arm which can respond to the increasing enhancement of the recording density of a magnetic disk apparatus and which have a high reliability, a method of producing such a magnetic head arm and an apparatus for producing such a magnetic head arm.
With a recent development of small-size and high-density magnetic disk apparatuses, the size of a magnetic head assembly for carrying a magnetic head has been reduced and in recent magnetic head assemblies, a signal pattern is formed on a suspension. Therefore, prevention of a breakage of a signal pattern during assembly is demanded. In addition, an improvement of the accuracy in mounting a magnetic head is demanded in order to realize a high recording density.
In a magnetic disk apparatus, a magnetic head is disposed on a single or both sides of each of a predetermined number of magnetic disks. A magnetic head is mounted on the end of a suspension, and the suspension is attached to the end of a carriage arm of an actuator assembly. Therefore, it is possible to position the carriage arm and, hence, the magnetic head at a desired position by moving the carriage arm in the radial direction of the magnetic disk by driving the actuator of the actuator assembly.
FIG. 17 is a plan view of the interior of a magnetic disk apparatus, and the reference numeral 1 represents a cover, and 2 a base. A spindle mechanism 3 is provided with a predetermined number of magnetic disks 4 which are arranged at predetermined intervals as recording media. An actuator assembly 6 which is freely rotated around a rotary shaft 5 is provided in the vicinity of the magnetic disk 4. In the actuator assembly 6, one side of the rotary shaft 5 is a driving portion (actuator) 7, and the other side is a carriage arm 8. The driving portion 7 is provided with a voice coil 9 for constituting a voice coil motor. The same number of carriage arms 8 as the number of magnetic disks 4 are provided and a magnetic head assembly 11 is attached to both sides or a single side of an engaging portion 10 at the forward end of the carriage arm 8 so as to position a magnetic head 13 at a predetermined position in the radial direction of the magnetic disk 4. The block composed of the actuator assembly 6 with the magnetic head assemblies 11 attached thereto is called a magnetic head arm.
FIG. 18A is a perspective view of the magnetic head assembly 11. The magnetic head assembly 11 has a suspension 12 produced by bending a sheet of a metal such as stainless steel at a predetermined angle, and the magnetic head 13 is fixed to the forward end of the suspension 12 by an adhesive. A caulking hole 14a is formed at a mounting portion 14 on the rear end of the suspension 12. A signal pattern 15 for transmitting record reproducing signals to the magnetic head 13 is formed on the suspension 12, and the forward end of the signal pattern 15 is connected to a terminal of the magnetic head 13. A lead terminal portion 16 is provided on the side portion of the mounting portion 14 of the suspension 12. The suspension 12 is further provided with a pin hole HL for receiving a positioning pin (not shown) when the magnetic head assembly 11 is attached to the actuator assembly 6.
The signal pattern 15 is composed of an insulation film 12b formed on the substrate 12a of the suspension 12, four conductive patterns (signal patterns) 15 formed on the insulation film 12a by, for example, etching copper (Cu) or the like, and an insulating protective film 12c (at most several .mu.m) formed on the insulation film 12b. A dummy pattern 17 is formed from a metal film having the same thickness as the protective film 12c on the portion other than the caulking hole 14a and the signal pattern 15 at the rear end portion of the suspension 12. A spacer 18 having a predetermined thickness is welded to the back surface of the mounting portion 14 at the rear end of the suspension 12 by spot welding by a laser or the like, as shown in FIG. 18C. A cylindrical protruding portion 19 is provided at the center of the spacer 18, and a through hole 19a formed in the protruding portion 19 communicates with the caulking hole 14a. When the magnetic head assembly 11 is attached to the carriage arm 8 of the actuator assembly 6, the protruding portion 19 fits into an insertion hole formed on the forward end of the carriage arm 8, as will be described later.
FIG. 19 is a plan view of the actuator assembly 6, and FIG. 20 is a perspective view thereof. The actuator assembly 6 is composed of a plurality of carriage arms 8 each of which is rotated around the rotary shaft 5 and the driving portion (actuator) 7, and an insertion hole 10a for attaching the magnetic head assembly 11 to both sides or a single side of the carriage arm 8 therethrough is provided at an engaging portion 10 at the forward end of each carriage arm 8. The driving portion 7 has the voice coil 9 provided on a coil support plate 7a and a flexible printed circuit board (FPC) 7c supported by a fixing portion 7b. The reference numeral 7d denotes a keep plate.
FIGS. 21A to 21C are explanatory views of the process of attaching the magnetic head assembly 11 to the carriage arm 8. FIG. 21A is a sectional view of the engaging portion 10 of the carriage arm 8 and the mounting portion 14 of the suspension 12 with the magnetic head assembly 11 attached to the carriage arm 8. The cylindrical protruding portions 19 (FIG. 18C) of the magnetic head assemblies 11 are fit into the insertion hole 10a formed in the engaging portion 10 of each carriage arm 8 from both sides of the insertion hole 10a, thereby producing an inlay portion clamps 31, 32 which are movable to both sides of the thus-produced inlay portion are provided, as shown in FIG. 21B. Each of the clamps 31, 32 is provided with a plurality of presser portions 31a (32a) which are arranged in the form of the teeth of a comb, and the upper surface of the presser portion 31a and the under surface of the presser portion 32a are tapered. When the presser portions 31a and 32a come into contact with each other, both tapered surfaces are in contact. In other words, the presser portions 31a and 32a are disposed in such a manner that when they approach each other, the tapered surface of a presser portion of one clamp comes into contact with the tapered surface of a presser portion of the other clamp and that when they approach each other, the inlay portion is clamped between the under surface of the presser portion 31a and the upper surface of the presser portion 32a.
As a result, when the clamps 31 and 32 move, the presser portions 31a, 32a are inserted between the engaging portions 10 of every two adjacent carriage arms 8 with the tapered surfaces in contact with each other, thereby vertically holding the engaging portions 10 in a fixed state, as shown in FIG. 21C.
In this state, a caulking ball 33 is pressed from above into the through hole 19a of the cylindrical protruding portion 19 with a caulking pin 34 through the caulking hole 14a of the magnetic head assembly 11. As the caulking ball 33 is pressed into the through hole 19a, the cylindrical protruding portion 19 is expanded so as to press the inner wall of the insertion hole 10a of the carriage arm 8. In this way, the magnetic head assemblies 11 are secured to the forward ends of the carriage arms 8, thereby producing a magnetic head arm.
In the conventional method of attaching a magnetic head assembly, the inlay portion is clamped between the under surface of the presser portion 31a and the upper surface of the presser portion 32a in order to hold the inlay portion in a fixed state. However, in order to clamp the inlay portion, the presser portions 31a, 32a slide on the surfaces of the mounting portion 14 at the rear end of the magnetic head assembly 11. Since the signal pattern 15 is formed on the upper surface of the mounting portion 14, the protective film 12c and the signal pattern 15 are unfavorably scratched by the surface protrusions of the presser portions 31a, 32a, or fine dust adhered to the surfaces of the presser portions 31a, 32a when they slide on the surfaces of the mounting portion 14. The scratch may lead to a signal error, and in the worst case, the sliding operation of the presser portions 31a, 32a scrapes the protective film 12c and cuts the signal pattern 15.